JP3904041B2 - Electrophotographic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic apparatus capable of printing images on both sides of a recording medium, such as an electronic copying machine and a printer.
[0002]
[Prior art]
When a normal electrophotographic apparatus is used in the double-sided printing mode, a recording paper that has completed the recording process for one side (hereinafter referred to as the front surface recording process) is recorded on the other side during conveyance (hereinafter referred to as back side recording). Reversed for implementation of the process). The recording paper reversal system at this time includes (1) reversing the recording paper and returning it to the paper feed tray, (2) switching back the recording paper, and (3) winding the recording paper around the reversing roller. Either one is often adopted.
[0003]
[Problems to be solved by the invention]
However, the above-described conventional electrophotographic apparatus has factors that cause curling of the recording paper being conveyed, such as the influence of heat from the two fixing rollers and a conveyance path bent to reduce the size of the apparatus. Specifically, as shown in FIG. 5, if the recording sheet is guided between the two fixing rollers and then guided to a straight path B, the recording sheet is not curled (b). Then, when guided to the curved paths A and C, the recording paper is curled according to the curved paths A and C (a) and (c). When the curled recording paper is conveyed, the recording paper is often not smoothly conveyed thereafter. Abnormal conditions that are likely to occur in the duplex printing mode with a long conveyance distance of the recording medium, such as jams, skews, and ear folds, are often caused by curling on the recording paper during conveyance. More specifically, when the recording medium is curled to the back side in the front surface recording process, jamming or the like is likely to occur in the resist portion for correcting the skew, or the transfer is performed in the subsequent back side recording process as shown in FIG. The recording paper is difficult to peel off from the body (transfer drum, transfer belt, etc.), and a winding jam or the like around the transfer body is likely to occur. Further, the winding of the recording paper around the transfer member can cause transfer failure due to excessive supply of transfer voltage.
[0004]
Therefore, it is necessary to suppress curling that occurs on the recording paper being conveyed, but it is difficult to do so because the thickness of the recording paper distributed in the market varies. This is because the recording paper has various curls depending on the paper thickness.
[0005]
Accordingly, a first object of the present invention is to provide an electrophotographic apparatus capable of smoothly transporting a recording medium. It is a second object of the present invention to provide an electrophotographic apparatus capable of smoothly transporting recording media of any thickness.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is an electrophotographic apparatus provided with a re-transmission mechanism that reverses the front and back of a recording medium discharged from a fixing device and retransmits the recording medium to a transfer drum and a transfer roller unit . A curl suppressing means for curving the recording medium discharged from the fixing device to a side opposite to a curve of a path through which the recording medium is guided; and a control means for controlling the curl suppressing means. A path switching member that is disposed at a branch point between the path to the discharge port side of the recording medium discharged from the fixing device and the path to the retransmission mechanism side, and selectively closes one of the two paths. And a guide member that guides the recording medium discharged from the fixing device to the branch point and provides deflection to the recording medium being guided to the branch point in conjunction with the path switching member. Provides an electrophotographic apparatus characterized that you controlling at least one of movement of said path switching member and the guide member.
[0007]
According to the present electrophotographic apparatus, curling generated in the recording medium due to the influence of heat from the fixing device is suppressed due to the deformation given to the recording medium by the curl suppressing means, so that the recording medium can be transported smoothly.
[0008]
In this electrophotographic apparatus,
If the control means controls the deformation amount of the recording medium in accordance with the thickness of the recording medium, the recording medium can be deformed according to the thickness, so that any thickness can be obtained. This recording medium can be smoothly conveyed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings.
[0010]
First, an outline of the overall configuration of the electrophotographic apparatus according to the present embodiment will be described with reference to FIG. However, here, an electrophotographic apparatus for color printing is taken as an example.
[0011]
The housing 5 of the electrophotographic apparatus is provided with a detachable cassette 12 for storing recording media 14 such as recording paper, and a discharge tray 20 on which the recording media 14 after image recording are stacked.
[0012]
Inside the housing 5, a controller (not shown) for controlling the entire apparatus, a recording medium conveyance mechanism for conveying the recording medium 14 from the cassette 12 to the discharge tray 20, and image formation with respect to the recording medium 14 being conveyed A recording unit for executing processing is incorporated.
[0013]
The recording unit is a photosensitive belt feeding mechanism that feeds the photosensitive belt 2 between the photosensitive belt 2, the two driven rollers 1b and the driving roller 1a in a predetermined direction, and charges the surface of the photosensitive belt 2 to a predetermined potential. A charging unit 3, an optical system box 4 that emits a laser beam 4 a for forming an electrostatic latent image of each color component on the charged photosensitive belt 2, and toner on the electrostatic latent image on the photosensitive belt 2. The respective color components (black, yellow, magenta, cyan) to be attached are superimposed on the developing devices 6 (K), 6 (Y), 6 (M), 6 (C), and the toner images of the respective colors on the photosensitive belt 2. The transfer drum 10a and transfer roller 10b to be electrostatically transferred to the recording medium 14, the AC static eliminator 17 for discharging the recording medium 14 to which the color toner image has been transferred from the transfer drum 10a, and the two recording rollers 14a, Sandwiched between 18b A fixing unit 18 for thermally fixing a color toner image to the recording medium 14, a cleaning blade 11 for removing the toner remaining on the photosensitive belt 2 after the toner image of each color is transferred to the transfer drum 10 a, and a recording medium 14 A drum cleaner 21 is provided for removing toner remaining on the transfer drum 10a after the color toner image is transferred. Incidentally, the developing devices 6 (K), 6 (Y), 6 (M), 6 (C) for the respective color components are provided on the photosensitive belt 2 on which electrostatic latent images of the corresponding color components are formed. A developing roller 6a to be contacted, a supply roller 6c for supplying non-magnetic one-component toner onto the developing roller 6a, and an elastic blade that forms a uniform toner layer on the developing roller 6a by frictionally charging the toner on the developing roller 6a 6d, a reset roller 6b for removing the toner layer on the developing roller 6a, and a conveying roller 6e for conveying the toner to the supply roller 6c side are provided.
[0014]
The recording medium conveyance mechanism includes a conveyance path of the recording medium 14, a plurality of rollers, a motor (not shown) that rotates each roller under the control of the controller, and the like. The configuration includes almost four conveyance systems, that is, A feeding unit for feeding the recording medium 14 from the cassette 12 to the recording unit, a discharging unit for discharging the recording medium 14 discharged from the recording unit (fixing device 18) to the discharge tray 20, and a discharging unit from the recording unit (fixing device 18). The recording medium 14 is divided into a retransmission section for retransmitting the recording medium 14 to the recording section, and a path switching section for switching the path of the recording medium 14 ejected from the recording section (fixing device 18). In both the double-sided recording mode and the single-sided recording mode, first, the recording medium 14 stored in the cassette 12 is sent out onto the conveying path by the rotation of the feeding roller 13, and the registration rollers 15 arranged in the conveying path are used. The skew is corrected by the rotation and sent to the recording unit (feed unit). The recording medium 14 discharged from the fixing device 18 is guided to the retransmission path side only when the back surface recording process in the double-sided recording mode is executed by the guide member 23 and the path switching member 7, and in other cases, Guided to the discharge path side (route switching section described later). Then, the recording medium 14 guided to the discharge path side is discharged to the discharge tray 20 by the rotation of the discharge roller 19 arranged in the discharge path (discharge section). On the other hand, the recording medium 14 discharged to the retransmission path side is sent to the reversing roller 8 by the rotation of the conveying roller 24 arranged at a plurality of positions on the retransmitting path, and is taken up by the reversing roller 8 during normal rotation. After that, the paper is retransmitted to the registration roller 15 of the feeding unit (retransmission unit) by the reverse rotation of the reversing roller 8 and the rotation of the pressing roller 9.
[0015]
Next, details of the path switching unit of the recording medium transport mechanism will be described with reference to FIGS. 2, 3, and 4.
[0016]
A guide member 22 that fixes the path of the recording medium 14 to a retransmission path and a discharge path is fixed to the inner wall of the housing 5. In addition, two support shafts 7a and 23a are fixed to the inner wall of the housing 5, and one of the support shafts 7a has a path switching for selectively closing either the retransmission path or the discharge path. A member 7 is swingably attached, and the recording medium 14 that has passed between the two heat rollers 18a and 18b of the fixing unit 18 is recorded on the other support shaft 23a at a branch point between the retransmission path and the discharge path. A guide member 23 for guiding the medium is swingably attached. Then, under the control of the controller, a solenoid (not shown) swings the path switching member 7 around the support shaft 7a. For example, when the back side recording process in the double-sided recording mode is executed, as shown in FIG. 2A, the path switching member 7 closes the discharge path by driving the solenoid. At this time, since the distal end of the path switching member 7 engages with the inner wall of the end of the guide member 23, the guide member 23 is inclined by an angle θ corresponding to the amount of displacement of the distal end of the path switching member 7. Accordingly, the recording medium 14 that is curved toward the retransmission path side is given a deflection in a direction that cancels the curvature immediately after being pushed out from between the two heat rollers 18a and 18b (that is, in a state where there is residual heat). . As a result, the recording medium 14 is smoothly conveyed on the retransmission path in an appropriate state without curling, and thereafter sent to the recording unit in an appropriate state without curling, as shown in FIG. On the other hand, in the case of the single-sided recording mode or when the back-side recording process in the double-sided recording mode is completed, as shown in FIG. 2B, the path switching member 7 closes the retransmission path by driving the solenoid. At this time, since the distal end of the path switching member 7 engages with the inner wall of the end of the guide member 23, the guide member 23 is inclined by an angle θ corresponding to the amount of displacement of the distal end of the path switching member 7. Therefore, the recording medium 14 that is curved toward the discharge path side is given a deflection in a direction that cancels the curvature immediately after being pushed out from between the two heat rollers 18a and 18b (that is, in a state where there is residual heat). . Thereby, the recording medium 14 is smoothly conveyed on the discharge path in an appropriate state without curling.
[0017]
In the present embodiment, the recording medium is bent on the side opposite to the curve of the path by the guide member 23, but the recording medium is bent on the side opposite to the curve 14 of the path by another member. It doesn't matter. In the present embodiment, the guide member 23 is moved by the path switching member 7, but it may be reversed, and the guide member 23 and the path switching member 7 are moved by separate drive sources. It doesn't matter if you make it.
[0018]
Incidentally, it is known that the curl generated in the recording medium 14 due to the influence of heat from the fixing device 18 has a correlation with the thickness of the recording medium 14. Therefore, in the present embodiment, a photo sensor for detecting the thickness of the recording medium 14 is provided at an appropriate position on the feeding path, or the thickness of the recording medium is designated by the user as described below. As described above, the amount of deformation applied from the guide member 23 to the recording medium 14 is controlled according to the thickness of the recording medium 14. The controller controls the inclination angle θ of the guide member 23 with respect to the common tangent of the two heat rollers 18a and 18b by driving the solenoid based on the detection value output from the detection circuit of the photosensor or the designation from the user. That is, for example, according to the relationship shown in FIG. 4, the controller controls the solenoid so that the thinner the recording medium 14, the greater the inclination angle θ of the guide member 23 with respect to the common tangent line of the two heat rollers 18a and 18b. Control. Thereby, whatever the thickness of the recording medium is used, it is possible to ensure smooth conveyance after passing through the fixing device. Assuming that recording papers of various thicknesses on the market are used, it is desirable that the guide member 23 be swingable up to about 30 ° to the left and right.
[0019]
【The invention's effect】
According to the electrophotographic apparatus according to the present invention, since the curl of the recording medium being conveyed is suppressed, Ru can be conveyed steadily recording medium.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a color electrophotographic apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a state in which a recording medium passes through a path switching unit of a color electrophotographic apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a state in which a recording medium passes through a recording unit of a color electrophotographic apparatus according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating a correspondence relationship between a thickness of a recording medium and an inclination angle of a guide member.
FIG. 5 is a diagram for explaining a relationship between a traveling direction and a state of a recording medium that has passed through a fixing device of a conventional electrophotographic apparatus.
FIG. 6 is a view showing a state in which a winding jam occurs on a transfer body (transfer drum) in a conventional electrophotographic apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a ... Drive roller 1b ... Follower roller 2 ... Photosensitive belt 3 ... Charger 4 ... Optical system box 4a ... Laser beam 5 ... Case 6 (K), 6 (Y), 6 (M), 6 (C) ... Each color Component developing device 6a ... developing roller 6c ... supply roller 6d ... elastic blade 6b ... reset roller 7 ... path switching member 7a ... support shaft 8 of path switching member 7 ... reversing roller 9 ... pressing roller 10a ... transfer drum 10b ... transfer roller 11 ... cleaning blade 12 ... cassette 13 ... feed roller 14 ... recording medium 15 such as recording paper ... registration roller 17 ... AC neutralizers 18a, 18b ... heat roller 18 ... fixing device 19 ... discharge roller 20 ... Discharge tray 21 ... Drum cleaner 22 ... Guide member 23 ... Guide member 23a ... Support shaft 24 of guide member 23 ... Conveying roller

Claims (2)

An electrophotographic apparatus having a re-transmission mechanism for reversing the front and back of a recording medium discharged from a fixing device and retransmitting the recording medium to a transfer drum and a transfer roller unit, the recording medium discharged from the fixing device, A curl suppressing unit configured to bend the curve opposite to a path along which the recording medium is guided; and a control unit configured to control the curl suppressing unit , wherein the curl suppressing unit discharges the recording medium discharged from the fixing device. A path switching member that is disposed at a branch point between the path to the exit side and the path to the retransmission mechanism side and selectively closes one of the two paths, and the recording medium discharged from the fixing device And a guide member that guides the recording medium being guided to the branch point in conjunction with the path switching member, and the control means includes the path switching member and the guide. Electrophotographic apparatus characterized that you controlling at least one of movement of the member.   2. The electrophotographic apparatus according to claim 1, wherein the control unit controls a deformation amount applied to the recording medium by the curl suppressing unit in accordance with a thickness of the recording medium. .

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